The present invention relates to fencing and particularly to fencing employing components formed of durable plastic (e.g., polyvinyl chloride) material.
The prior art includes fencing systems that utilize sleeve or covering structures for cladding associated wood fence posts and rails. See, e.g., Teasdale U.S. Pat. No. 5,480,126 and Miller U.S. Pat. No. 5,458,942. Various configurations of the cladding components are shown in those patents. It is seen that in each, the entire outer circumference of the posts and rails is covered by the wrap.
It is also known to form tongue and groove fence uprights of hollow tubular plastic, and to provide interlocking fence panels serving to conceal points of attachment. Lancer, Sr. U.S. Pat. No. 5,529,289 discloses fence panels which are interlocked in an overlapping shingle-like fashion along a fence line. The end structure of one panel overlays, and thus conceals, the fastener securing an adjacent panel to the horizontal rails. Edgeman U.S. Pat. No. 5,702,090 discloses a plastic fencing system utilizing post and rail structures formed of hollow extruded plastic tubes, as well as hollow tubular plastic uprights ("pickets"). FIG. 6 of that patent shows a hollow picket with a tongue and groove configuration which allows the pickets to be interlocked with each other, as seen in FIG. 2. The pickets or uprights are secured within slots extending along inner faces of upper and lower rails. Center rails and brackets may also be installed.
Parth U.S. Pat. No. 5,725,201 discloses, similar to the Lancer, Sr. patent, fence panels that interlock with each other within a framework constructed of tubular posts and upper and lower rails. By virtue of the play provided in the interlocking end structures (see FIGS. 3 and 4 of that patent), the overall length of the panels assemblies can be laterally adjusted to account for variations in post-to-post distances.
Known systems employing plastic components, as described above, hold out the prospect of increased durability and reduced maintenance as compared to all-wood fencing. However, the known systems have certain drawbacks in terms of their design. For example, the cladding of the Teasdale and Miller patents does not, unless it is oversized, allow for temperature induced expansions of the wood posts and rails. As a result, bulging or detachment of the cladding may occur. Oversizing of the cladding to avoid this problem is generally undesirable from a structural standpoint, and also because it results in greater material usage and costs. In addition, since the entire circumference of the fence posts and rails are covered with the cladding, it is not possible, once the cladding is installed, to attach the rails to the posts, and the uprights to the rails, with pass-through fasteners such as nails or screws, without driving the fasteners through the cladding layer. Driving a fastener through the cladding material creates a point of fixation restricting relative movement of the cladding and underlying wood. This can result in bulging, warping, tearing and/or cracking of the cladding due to disparate temperature induced expansions/contractions of the wood and plastic material. Separate through-holes can be provided, but this requires an additional manufacturing step. In the fencing system of the Teasdale pates, complicated members are provided as integral parts of the sleeve structures, to allow for connection of wall-forming panels without the need for pass-through fasteners. While potentially avoiding the aforementioned expansion/contraction problems, such complicated structures drive costs higher, due to increased material requirements and/or additional manufacturing steps.
A fencing system rendering more cost-effective the use of plastic components to improve the durability, and decrease the maintenance, of conventional wood fencing would be highly desirable. Equally desirable would be a fencing system utilizing plastic components allowing construction of a hybrid wood/plastic fence having an attractive appearance more closely resembling an all-wood fence.